A major focus of my laboratory is to understand the events that must occur to transform a normal human cell into a cancer cell. Much of our knowledge of this process, at a biochemical level, comes from experiments in which the effects of oncogenes and tumor suppressors are analyzed in rodent cell culture systems and in intact model organisms. However, it is clear that these models do not perfectly reflect the transformation process in humans. In fact, it is impossible to transform normal human cells using the same combinations of oncogenic alterations that are effective in rodent cells. Our efforts over the last several years have been aimed at the development of genetic strategies to address aspects of this problem in cultured mammalian cells and in cells derived from model organisms (e.g. Drosophila). Through these efforts, we have identified a combination of viral and cellular oncogenes (E1A, HarasV12 and MDM2) that can transform nomnal human fibroblasts into cells that are tumorigenic in nude mice. The experiments proposed herein use this experimental paradigm to define the cellular pathways that are altered to achieve conversion of a normal human cell into a cancer cell. Specifically, we will use combinations of mutational analysis and genetic complementation to define the roles of E1A and MDM2 in the transformation process. Through these efforts, we hope to achieve a more complete knowledge of the processes, which lead to the development not only of human cancer but also of lethal metastatic disease.